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91.
The reaction of 1-alkynylcyclobutanols with aryl iodides in the presence of Pd(OAc)2 and Et3N in acetonitrile at 80°C for 24 h gives 2-disubstituted methylenecyclopentan-1-ones in modest to good yields. The tandem insertion-ring expansion process proceeds via the formation of an alkynyl π-complex, followed by migration of a carbon-carbon bond of the tert-alkanol to form the cyclopentanones stereoselectively. 相似文献
92.
A de novo asymmetric synthesis of the octahydroisobenzofuran skeleton contained within the eunicellin family of natural products has been completed. The key transformations involve the convergent assembly of a tetrasubstituted tetrahydrofuran by condensation of a functionalised allylsiloxane with an aldehyde; controlled epimerisation of a C4 aldehyde by intramolecular trapping; installation of the isopropyl substituent by stereoselective Michael addition to a 5,5-bicyclic enone; and ring expansion of the 5,5-system to the target structure by radical-mediated cyclopropane fragmentation. 相似文献
93.
94.
Ksenia Shilyaeva Nils Elander Evgeny Yarevsky 《International journal of quantum chemistry》2007,107(6):1301-1315
Peaks in collision cross sections are often interpreted as resonances. The complex dilation method, as well as other methods relying on analytic continuation of the scattering formalism, can be used to clarify whether these structures are true resonances in the sense that they are poles of the S‐matrix and the associated Green function. The performance of the Mittag–Leffler expansion and T‐matrix Green function expansion methods are formally and computationally compared. The two methods are applied to two model potentials. Eigenenergies, s‐wave residues, and cross sections are computed with both methods. The resonance contributions to the cross sections are further analyzed by removing the residue contributions from the Mittag–Leffler and Green function expansion sums, respectively. It is suggested that the contribution of a resonance to a cross section should be defined through its S‐matrix residue. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
95.
There have been many experimental and theoretical studies on molecular conduction, as it is a fundamental parameter in the study of molecular‐scale electronics. We have investigated the features of molecular conduction using a Green's function method, which has often been used to solve problems in quantum transport and is also effective in elucidating electron transport in molecules. We have obtained the novel effective Green's functions, including the first‐order energy corrections, by accommodating the self‐energy of the electrodes as perturbation terms. Although these approximate Green's functions only provide information on the first‐order energy corrections, they can involve the elementary properties of molecular conduction. We propose a scheme for the analysis of the relations between molecular orbitals and their roles in molecular conduction and present analytical calculations for normal and cyclic polyenes. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献
96.
The electrophilic iodocyclization reaction of (Z)- and (E)-5-n-alkylsubstituted 4-alken-1-ols followed by base-induced hydrodeiodination reaction stereoselectively gave, respectively, (Z)- and (E)-alkylidentetrahydrofurans in high yield. Completely different outcomes were observed with (Z)- and (E)-6,6-dimethylhept-4-en-1-ol: their iodocyclization furnished, respectively, threo- and erythro-2-(1-iodo-2,2-dimetylpropyl)tetrahydrofuran with high stereoselectivity. The threo isomer gave clean formation of 6-tert-butyl-3,4-dihydro-2H-pyran by base-induced ring expansion, while erythro isomer underwent a base-induced ring contraction to 1-cyclopropyl-3,3-dimethylbutan-1-one. Moreover, (Z)- and (E)-5-cyclopropylpent-4-en-1-ol underwent a 6-endo-iodocyclization to threo- and erythro-2-cyclopropyl-3-iodotetrahydro-2H-pyran, respectively, that under the same basic treatment, gave two isomeric 6-cyclopropyldihydro-2H-pyrans in a stereoselective fashion. 相似文献
97.
阶梯扫描伏安法与线性扫描伏安法相关性的理论研究——简单可逆体系 总被引:1,自引:0,他引:1
本文采用Reimann-Stielties(黎曼-斯堤杰斯)级数展开法,指导了简单可逆电极体系的线性扫描伏安法和阶梯扫描伏安法的电流方程式,得到了能有机地统一的这两种最大为基本的伏安法的电流函数表达式,表达式简明直观,在无因次电流函数的基础详细讨论了制约阶梯扫描伏安法和线性扫描伏安法之间相关性程度的各因素,获得了一些新的结论。 相似文献
98.
L. G. Voskressensky S. V. Akbulatov T. N. Borisova A. V. Kleimenov A. V. Varlamov 《Russian Chemical Bulletin》2007,56(11):2323-2329
A reaction of substituted hexahydroazepino[4,3-b]-and-[3,4-b]indoles with activated alkynes was studied. A one-step method for the synthesis of isomeric hexahydroazonino[5,6-b]indoles different by positions of the double bond in the azonine ring was developed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2244–2250, November, 2007. 相似文献
99.
Christoph NeumannAndrea Prehn Junquera Cathleen WismachPeter G Jones Rainer Streubel 《Tetrahedron》2003,59(33):6213-6220
Catalytically-induced ring expansion of 2H-azaphosphirene complex 1 using ferrocenium hexafluorophosphate and acetone (2), diethylketone (3), cyclohexanone (4), benzaldehyde (5) or para-hydroxy-benzaldehyde (6) furnished selectively the Δ3-1,3,5-oxazaphospholene complexes 7-11, whereas with ortho- and para-hydroxy- or ortho- and para-amino-substituted benzonitriles the 2H-1,4,2-diazaphosphole complexes 16-19 were obtained. Two further findings are noteworthy: (1) The significant decreased reaction time in the case of the sterically more demanding carbonyl derivatives 2-4 and (2) the formation of diastereomers in the case of 10 and 11 with a ratio of 8:1 and 9:1, respectively. All products were characterized by NMR, MS and elemental analysis and the configuration of complexes 7 and 10a were determined by X-ray single-crystal diffraction analysis. 相似文献
100.
Densities and sound velocities of binary mixtures of cyclohexanone, 2-butanone, 1,4-dioxane and 1,2-dimethoxyethane were measured
at 298.15 K and also the densities at 303.15 K. Excess volumes were determined from densities. Isentropic compressibilities
were determined from densities and sound velocities, and excess thermal expansion factors were determined from excess volumes
of two temperatures. Excess isothermal compressibilities and excess isochoric heat capacities were then estimated using excess
isobaric heat capacities previously reported. Excess volumes and excess isentropic and isothermal compressibilities were negative
except for cyclohexanone+1,4-dioxane system.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献